1. Field of the Invention
The present invention relates to a device for coating granular solids such as tablets, catalyst-carrying particles and so on.
2. Brief Description of the Prior Art
Japanese Patent Publication No. 43 475/78 discloses a rotary drum type device for coating granular solids. In this device, a rotary drum comprises a cylindrical section with the wall perforated so as to permit the flow of air into and out of the rotary drum, and side walls contiguous with the cylindrical section. One side wall is formed with a charging and discharging opening while the other side wall is rigidly connected to a rotary or drive shaft which in turn is rotatably supported on a supporting frame or yoke and is drivingly connected to a prime mover through a suitable power transmission mechanism. An annular duct which is mounted around the cylindrical section of the rotary drum is divided into a lower space which serves as a gas supply passage and an upper space which serves as a gas exhaust passage. This air duct is provided with a pair of hollow tilting shafts which are diametrically opposed and radially outwardly extended and whose axes are at right angles of the axis of the rotary drum or the rotary shaft. These hollow tilting shafts are communicated with the gas supply and exhaust passages, respectively, and are rotatably supported on supporting stands. The gas supply passage is communicated through one tilting shaft with a blower disposed within one supporting stand while the gas exhaust passage is communicated through the other hollow tilting shaft with an exhaust fan or the like disposed in the other supporting stand. Therefore the air or suitable processing gas may continuously flow through the rotary drum during the coating operations. There is provided a tilting mechanism which is operatively connected to one of the tilting shafts so that the rotary drum may be tilted relative to the vertical about the axis of the hollow tilting shafts. That is, in the case of the coating operations, the axis of the rotary drum may be maintained horizontal so that the charging and discharging opening may be in the horizontal position, but in the case of the discharge of the product solids, the rotary drum is tilted so that the charging and discharging opening may be directed downwards and consequently the product solids may be completely, quickly and easily discharged out of the rotary drum.
However the rotary drum type coating device of the type described is not provided with a mechanism which may adjust the height of the rotary drum. It is desired to bring the rotary drum as closely to the floor as possible in the case of the inspection, maintenance and adjustments of the component parts in the rotary drum and of the charging of process solids. Furthermore it is also desired to adjust the height of the charging and discharging opening of the rotary drum, which is directed downwards in the case of the discharge as described above, depending upon the height of a product solid receiving vessel or the like so that the complete, quick and easy discharge may be ensured.
The rotary drum type coating device of the type described is further disadvantageous in that it is not provided with suitable thermal insulation means so that the heat of the hot air or the like forced into the rotary drum may be quickly dissipated to the surrounding air. As a result, saving in thermal energy cannot be attained and the drying efficiency is low.